Method of lug strap manufacture



Sept. 23, 1941. H. M. BACONr v 2,256,701`

' METHOD OF LUG STRAP MANUFACTURE Filed Feb. 2s, 193s Gttomegs Patented Sept. 23, 1941 METHOD OF LUG STRAP MANUFACTURE Henry M. Bacon, Dayton, Ohio, assignor to The Dayton Rubber Mfg. Company, Dayton, Ohio, a corporation of Ohio Application February 23, 1938, Serial No. 192,116 11 claims. (ci. 13o- 153) This invention relates more particularly to improvements in lug straps of laminated construction wherein superposed plies of fabric are united by a bonding material to form the strap.

Important objects of the invention are, to provide a very durable lug strap of the said character; to provide such a strap constructed for even distribution of working stress throughout the different plies of fabric; to provide for improved simplied construction of the bend or bow portion of such a strap; and to provide an improved lmethod of making a lug strap of the said laminated type.

Other objects of 'the invention will appean hereinafter.

In the drawing,

Figure 1 is a perspective view of a core member employed for Winding thereon a fabric sheet coated with a bonding material, as a step in lug strap manufacture;

Figure 2 a cross sectional View of the said core and showing diagrammatically the fabric wound therearound;

Figure 3 a plan view of the sleeve formed by the Wound fabric, with dot and dash lines indicating the transverse severing of the sleeve to form a multitude of double straps;

Figure 4 a sectional view showing the molding of a double lug strap;

Figure 5 a transverse section on the line 5-5 of Figure 4;

Figure 6 a plan view of a molded double strap;

Figure '7 a perspective view of a finished single strap;

Figure 8 a partial sectional view similar to Figure 4, but on a central plane at a right angle thereto as at line 8 8, showing the molding of a double lug strap with integral convex cushions within its bends;

Figure 9 a detail sectional view of an end of the mold core, taken on the line 9--9 of Figure 8;

and then bend and mold the roll so formed into the desired U form. In the employment of any of said materials the bending thereof into U-shape materially impaired their strength owing to the fact that the material at the outside df the bend would be stretched and the material at the interior of the bend would be compressed or cramped. Consequently the lug strap would be incapable of uniformly distributed resistance to working stress and its life would be materially shortened. Particularly in the case of straps constructed of fabric and glue some layers of the fabric became stretched and others became wrinkled so that only the middle layers were in a normal condition of tension, with consequent concentration of stress and injurious strain. Efforts were made to overcome this defect but they involved laborious and costly methods of construction and failed `to avoid liability of flawed construction. The employment of glue in the structure of the strap is also objectionable yfor the reasons that the glue tends at times to soften under the humidity of the weave room and at other times it cracks under the shocks and flexure to which the strap is subjected in service and in handling.

My invention overcomes the defects noted and provides a strong, durable lug strap by a con-` venient and ycomparatively inexpensive method for manufacturing lug straps in large quantities and with minimum liability of flawed construction. The invention also provides a lug strap made of such material as to render the strap free from vattack by rodents and having other advantages which will appear hereinafter.

Further by my method of making lug straps no metal embedding reinforcing members are required. The use of metal reinforcing members and the like embedded within the strap body has a tendency to set up undue strains causing the body of the strap to segregate therefrom and accelerate the failure of the strap. Aside from this, my method avoids the necessity of using shorty plies of fabric, as heretofore employed in making lug straps, in order to build up thickness at de In my improved sired sections of the strap. methodr the desired thickness is built up at the bow of the strap by heat flowing under pressure of the rubberized fabric material ,during molding, as hereinafter disclosed..

In the manufacture of lug straps embodying the improved construction I select a wide sheet I of square-woven textile fabric with maximum warp strength and'with pick strength consistent with easy handling. Both sides of this sheet I coat with a bonding material 2 which is prefer. ably a rubber composition capable of being vulcanized to a hard state andhaving a low viscosity prior to vulcanization. Other bonding materials having the required thermo-flowing and setting properties rnay be employed butv rubber is preferred, for reasons which will appear hereinafter.

The sheet l, .coated with the rubber composition is wound around a core 3 whose cross section `conforms substantially to the interior of an elongated loop such as would be defined by placing Vtwo U-shaped lug straps end to end. 'I'he side edges-of the core are rounded, as at 4, in

' accordance with the Vcurvature of the `interior Vof the bend or bow of the lug strap. An oak plank v so formed will serve satisfactorily for the core; As the sheet is wound it is kept suciently taut for smoothness, and the Winding-'islcontinued-to form a number of superposed-:plies Vsufticientto Ybuildthe structure up to aldesiredthickness exceeding that of the iinished lug strap. The sheet should be woundwith its warp threads or strands, Y designated W in Figure 3, running straight-and parallel around the core 3. sheetV `I is formed into aflat, multi-plysleeve with-theplies lying smoothly one upon another.

This-sleeve'fisremovedfromthe-Ycore l Yand severed along rthe transverse-linesA 5Y equally Yspacedalong*v the lsleeve to'thereby provide a'multitude i ofjfelongated iiatvv loops feachY conforming sub.v

stantiallyto 1a*Y pair of lugstraps arranged end-to end. Preferably the Width of these, partly formedcdouble straps cut from the sleeve, thatA isggtheirwidth between the lines 5 is about oneY thirty-second of an inch less than that desired forthei'lnis'hed strap. Y

'Each double strap isine'Xt subjected'to a mold- Y ing fand preliminary vulcanizing operation, This Thus the coatedv moldingandvulcanizing operation is performed to imold'the Ustrap tothe desired shape and cross sectional dimensions, bondV together the plies andvulcanize the Vrubber vcompositionto a preliminary'softL rubber state. Y g In preparation for` the'molding Vand-vulcanizing operation a moldcore 6 of steel'or ,other suitable materialV is'fitted into the loopv defined :byithe'rdouble strap.,l This'core'should'have precisely thesh'apeand dimensions desired Yfor the interiorr of `the strap.- As shown, the core hasy flat' sides and properly roundedends.A The strap and core'l are placed betweenv opposed blocks 4'lV of'a' split' mold. Said blocks have in'theirofp- -posed f aces' elongated cavities y8Y with' rounded ends and'conform exaotly'to Vthe desired shape and dimensions .ofthe "exterior ofthe strap, The plane"of'separationof the vb-locks occurs at the center'ofjthe'bends of the strap, and the dimensions 'of' the cavities 8 :and of thecore 6 are so to form two single straps S. Also, theusual slots Y v 9 are made in the legs of the strap either before or after severance. Finally the Vulcanization Vof the rubber is completed to bring it to a hard state. This may be doneby subjecting the completely formed straps to dry heat in a suitable oven.

In a-v modification of the above 1- preferred method of manufacturing lug straps `I may eliminate the preliminary soft rubber vulcanization Y step and yvulcanize the double strap to a hard rubber state and thereafter sever, "trim and slot vthevU-shaped lugl strap in the usual manner.

This procedure enables me to effect a decided saving in the. costof manufacturing the lug straps, however, where the highest quality of lug straps is desired the former method should be employed.' Itis possible, also, whereV the lug straps do not have to conform to exact dimensions, torform the U-shaped straps, and trim and slot 'themprior to vulcanizing them to a hard state.

The employment-` of the materials and Ythemethod described produces: asuperior strap Whichfsatisesall service requirements. Hard rubber is a very satisfactory material because of its mon-brittle nature, itshigh-tensile strength,` its -imperviousness to weaverroom-humidity and also because rrodents'will not eat-V it. Thezarrangementof the fabric with its'rwarp--threadsrunning lengthwis'eof-y the strap contributes-,to

:tensile strength, and the manner-in'which-thecoated fabric is preformed into'straps'b'y'continuous, smooth winding of the sheetv I ensures even distribution of tension throughout all of the plies. It will be obvious that the preforming'operation is performed in amanner tor-'reduce liacorrelated vthat"whenthe mold is closed the space de's'ethan the'leg-f'ormingportions. The pres'.

sure throughout theentire strap is Vsuiiiierit to unitethe'plies intimately and evenly.` s

Themolded doubleistrapis next removed'from the' mold," the? core `jisf withdrawn, the strap vis cool d1 and'excesfs," overow rubber j is Ytrimmedof" The double" strap is'severed in* ,the middlebility'of unevenness inthe plies'to-a minimum. 'I'he usualstretching of the pliesfa't theA outside of the bow of the lstrap and the cramping" and buckling of the plies at the innerl side ofthe Vbow is entirely avoided in asimple mannerVV by my preforming method. Substantially' alli fabric i plies employed inthe structure of the'l strap Yextend continuously tljnjoughout'n the length ofboth` legs of "the strap and around; .thei bow. Y Af' desired excess thickness ofthe bowvof' the Ystrapjs' obtained by owing-excess bondingimaterial-into the bow. Y This avoids employment'of short plies The thickened bow-provides the requiredcushioning' effect.v Also; while of less densitythan the'legs of the strap the bow has adequatetotal' strength due to its increased'thickness.

h Due tothe factlthat the fabric is coatedzupon both sideswithth'e rubber compositionV andth'at thecompositionis coniined'in'ther molding operation then-finished ,strapcontains much more of theA composition thanisrequired for mere bond-j ing. I t comprises a large part :ofthegstrapyas shown, and formsaitough'rubberi body envelopingth'e fabric; ThisY produ-cesa lug strap which is hard, tough, non-friable, flexible and moistureimpervious. The rubbergsurrounds'th'e individual threads of the fabric; and is reinforced throughout; thefstrap by the fabric '.pliesf Ifaplug; not shown,A isfrequired for theinteriorv of-theb-bow ofv the'strapit may be fitted,` drilled andriveted-into place: y

`It is also possible Vtol'forma satisfactory'con'- Vex: cushion in the bowtofrrthefstrap;in; a very simple manner. This may be doneas shown in Figure Y 8 f by l provisionv of a mold core 6a similar to the core-exceptthat v,it has' Aconcave en dsfb conforming to the"desired-shapeoftle cushion:V

The molding pressure causes the fabric and excess bonding material to fill the concavities of the core and form the integral cushions I0. Otherwise the strap with the convex cushion is formed in precisely the same manner as the strap previously described.

This application is a continuation in part of my copending application Serial No. 68,534, filed March 12, 1936, and issued as Patent No. 2,119,479, May 31, 1938.

It is, of course, understood that my invention is notl limited to the exact structure of the article disclosed and defined by the claims since obvious modifications within the scope of this invention may be made by those skilled in the art.

Having thus fully described my invention what I claim as new yand ydesire to secure by Letters Patent is:

l. The method of making a lug strap for weaving looms, comprising providing a sheet of fabric coated with bonding material in excess of they amount required merely for bonding, winding said sheet smoothly a plurality of times around a core to produce a multi-ply sleeve conforming substantially in cross section to the elongated loop form of a pair of lug straps arranged end to end, severing said sleeve crosswise into widths approximating the width of a llug strap to thereby provide a plurality of double lug straps, inserting a mold core into the elongated loop defined by each double strap and subjecting the double strap to molding pressure directed to compress the elongated sides of the double strap normal to the plane of the plies to a greater degree than the bends of the strap forcing excess bonding material into the bends to render them thicker than the sides, severing the double strap to form single U-shaped lug straps, and curing the laminated body to form a hard integral strap.

2. The method of making a lug strap for weaving looms, comprising providing a sheet of material of a width several times that of a lug strap with bonding material, winding said sheet smoothly a plurality of times continuously around a core to produce a multi-ply sleeve conforming substantially in cross section to the elongated loop form of a pair of lug straps arranged end to end, severing said sleeve transversely into widths approximating the width of a lug strap to thereby provide a plurality of double lug straps, uniting the plies in each double lug strap .by employment of a bonding material and subjecting the double strap to a molding operation so as to force bonding material to fiow into the bow portions so as to build up the thickness of the double strap in the bends ras compared with the inter-connecting portions, severing the double strap to form single lug straps, and curing the straps to produce a tough abrasionresistant product.

3. The method of making a lug strap for weaving looms, comprising winding plies of fabric coated with moldable material lfor bonding the plies in superposed relation on a core shaped to conform generally to that of a nished ldouble lug stra-p and with said bonding material in excess of that required solely for bonding the plies, and then subjecting said -assembly to molding pressure directed and gauged to compress the legs of the strap normal to the plane of the plies to a greater .degree than the bow of the strap and force excess bonding material into the bow to render it thicker than the legs, and forming a convex cushion portion integral with the bow at the inner side of its bend.

4. The method of making U-shaped lug straps, `comprising the steps of winding aY rubberized sheet about a core to forma number of superposed plies thereon, removing said core therefrom forminga sleeve andrsevering the superposed plies constituting said sleeve alongan axis transverse to the longitudinal axis of said sleeve to form a plurality of elongated flat loops of the desired thickness, subjecting said loops to a preliminary molding and vulcanizing treatment whereinthe plies are bonded together to form soft rubber loops having reinforced bow sections, said reinforced bow sections being effected by subjecting the leg portions of the strap to greater pressure than said bow sections during molding to force ,excess rubber to flow into the'bow portions increasing the thickness of the bow portion, removing the preliminary treated loops from the mold, severing therloops in the middle, trimming and slotting them to form a plurality of U-sh'aped straps, and finally completing the'vulcanization of the straps to a hard rubber state.

5. The method of making U-shaped lug straps, comprising the steps of winding a rubberized sheet about a core to form a number of superposed plies thereon, removing said core therefrom and severing the superposed plies along an axis transverse thereof to form an elongated fiat double strap loop of the desired thickness, subjecting said loop to a preliminary molding andy Vulcanizing treatment wherein the plies of said double strap are bondedA together to form a soft rubber loop having the bow sections thicker than the intermediate portions, said thicker bow sections being eifected by subjecting the leg portions of the strap to a greater pressure than said bow section during molding to force excess rubber to flow into the bow sections, removing the preliminary treated loop from the mold, severing the loop in the middle to form two single U-shaped straps, trimming and slotting same, and finally completing the vulcanization of the U-shaped straps to -a hard rubber state.

6. The method of molding a lug strap for weaving looms, comprising winding plies of square-woven textile fabric :coated with excess bonding material around a lcore to form a sleeve conforming substantially in cross section to the elongated loop formed by a pair of lug straps arranged end to end, severing said sleeve crosswise thereof to provide a double lug strap member and molding said double strap under heat and pressure while subjecting the leg-forming portions of the strap to greater compression than the bends forcing excess bonding material from said leg-forming portions into the bends to make them thicker and less dense than said leg-forming portions.

7. The method of making lug straps for weav- ,ing looms from laminated plies of fabric coated with vulcanizable binding agent, comprising winding a rubberized sheet of fabric around a core to form 'an elongated loop conforming to a pair of lug straps arranged end to end of the build up plies, severing said elongated loop transversely thereof to provide a double lug strap member, molding said double strap under heat and pressure while subjecting the leg-forming portions of the strap to greater compression than the bends forcing some of the bonding material from said leg-forming portions into the bends to make them thicker land less dense than said leg-forming portions, thereafter severing the double strap in half ing the same to a hard, exible state.

`singlelug straps. f

9. Y The methodgof ,fmakinga lugstrap forfweav-` ing looms,A comprising-providinga -sheetoffabric form of ya pair of lug Vstraps arranged end toend', severing.y said sleeve into widths approximating the desired width-of a lugrstrap to 4thereby provide a pluralityA ofdouble lug straps, inserting lanY elongated -mold -core into the elongated loopV del fined by; each-double c strap, subjecting the' double strap to a molding operation and, insaid moldingy operation, subjecting the elongatedl portions intermediatethe bows of the double -straptoplessurefsufiicient to force *plies therein.closer-eto-V gether thanfr the -p1ies-.ir;1A the 'bows of theY strap Y andfthereby force excess bonding material from betweenV the pliQSp-of saidv intermediate portions,

and causing itto now intothe bows to renderv thefbows thicker than thefsides lto reinforce the sama-and severing^ the donble 'strap--to obtain coated-upon both-faces with bond-ing material, Winding -said' sheetsmoothly a plurality of f times around a core tofproducea multi-plygY-sleeve con- -Y forming substantiallyincross-section to the-e1ongated loop formofafpuair of lug straps larranged endeto,endLsevering'said sleeve into widths approximating Y the desired width of a lug 4strap to inserting an` elongated mold core into the elongated; loop defined byeach double strap, subjectingrthe double strap'to v-a molding operation and in/said-molding operation stlku'ecting-Y the elongated sides of the Vdoublestrap to pressure directedl normal to fthe planeof `theplies thereof Y toA force'rsaid pliesrcloser together than theplies in the bows of the strap thereby forcing excess A therebyprovideafplurality of double lugstjraps,

' than the legsltoprovide it with more bonding.

bonding material from betweentheplies of saidk 'Weaving coated'uponk both-faces with rubber bonding ma@V teriaL*y laxzingrsaidV fabric in superposedplies` around a core to form the legs; and bow of a Y lug-strap; arrangingVY said fabric so that thecwarp threads ftherefgez'ztend lengthwiseof the legs yandsides;r and causing; said excess bonding- -material-f toalowabetweenathepliesfof the Lbows,Y to render thefbows thicker;than the. sidesfor vthe pur-pose setfprthylandsevering the y*double strap to obtainV singleflugstraps. l v

10. The method of making a 1ugstrapfo1: looms, comprising-v providing fabric around Vthe bow, subjecting thevstra'p to a lmolding'` and vulcanizingoperation and, in said operation, subjectingfthe legs'of the vstrap .to pressure directed. normal .tov the plane ofthe plies inthe legsv to force. theleg`V plies closer together thanA the plies inthe bow and thereby forcev excess.

bondingmaterialfrom betweenrthe leg pliesi and causing said, excessbondingl. material tov ow -be tweenlthe plies, in'- the, bow, to render 1 the bowf thicker than thewlegs ,and 4provide it withmore bonding. materialin` proportion rto fabric, for .the Y purpose setforth. Y Y v Y Y o 11--. 'Il1e.method of 'makingy adug s trap` for weavingloomsQcomprising; providing fabric coated with rubber, bonding material in i excess of the amount required merely for bonding,A lay'- ing-.saidifabric in lsuperposed plies to form the legs and bowofa lug strap,l subjecting the strapl toy a Ymolding and. vulcanizingY operation and in said operation subjecting the legsy of the strap to pressure Vdirectednormal to the plane of the pliesl in the.V legs tofforce them closer together than the plies inthe bow thereby forcing excess bonding material 'from between the leg plies, land causing Y said excess bonding material VVto flow into the bow 'ofl the strap rendering the Abow thicker' materialgirrproportion` to fabric, for the purpose set forth'. A

HENRYVA M: BAcoN 

